Philippine police are investigating as a criminal matter a fire that killed at least 72 factory workers who became trapped in the building’s second floor, where a relative said iron grills on windows prevented the victims from escaping.

All bodies were believed to have been retrieved from the gutted two-story Kentex Manufacturing Corp. rubber slipper factory, a day after the fire raged for over five hours in the Manila suburb, said Valenzuela city police chief Rhoderick Armamento.

The focus shifted to identifying the bodies and investigating the cause of the blaze, he said.

At a village hall, 69 bodies were lined up as relatives wearing surgical masks streamed in batches to try to identify the charred remains through jewelry or other personal items. Three victims were identified earlier.

Among the questions being raised are if the factory followed fire and building safety standards.

Dionisio Candido, whose daughter, granddaughter, sister-in-law and niece were among the missing, said iron grills reinforced with fencing wire covered windows on the second floor that “could prevent even cats from escaping.”

He said authorities allowed him to enter the gutted building, where he saw charred remains “piled on top of each other.”

Relatives told local media their kin sent frantic text messages asking for help from second floor before contact was lost.

Police will file charges against “all those accountable and those at fault,” said police Deputy Director General Leonardo Espina.

Interior Secretary Mar Roxas said the city’s fire marshal and two other fire department officers were relieved of duty.

One of them, fire marshal Mel Jose Lagan, had earlier told reporters that arson investigators will look into why the people were unable to escape from the second floor when there was a “sufficient exit” that includes a wide stairway to the back of the building leading to the outside. They will also look into whether there were more people inside the building than allowed.

Iron grill bars on windows are common in offices, factories and homes in the Philippines to keep away thieves. In workplaces or factories, they are also meant to prevent employees from stealing equipment or products.

Mayor Rex Gatchalian said that a workers log book was lost in the fire and the foreman was among the dead, making it difficult to determine how many were inside the factory at the time.

Gatchalian said the fire was apparently ignited by sparks from welding work at the factory’s main entrance door, triggering an explosion of the chemicals used to make the slippers. Workers fled to the second floor where they were trapped, he said.

District Fire Marshal Wilberto Rico Neil Kwan Tiu said that the building had other exits but apparently the workers were overwhelmed by the thick black smoke from the burning rubber and chemicals, which are highly flammable and caused the blaze to spread quickly.